allow encrypting watch-only wallets. initial support for hw wallet storage encryption.

plugins/hw_wallet/plugin.py

@@ -51,3 +51,10 @@ class HW_PluginBase(BasePlugin):
         for keystore in wallet.get_keystores():
             if isinstance(keystore, self.keystore_class):
                 self.device_manager().unpair_xpub(keystore.xpub)
+
+    def setup_device(self, device_info, wizard, purpose):
+        """Called when creating a new wallet or when using the device to decrypt
+        an existing wallet. Select the device to use.  If the device is
+        uninitialized, go through the initialization process.
+        """
+        raise NotImplementedError()

plugins/hw_wallet/qt.py

@@ -70,9 +70,10 @@ class QtHandlerBase(QObject, PrintError):
         self.status_signal.emit(paired)
 
     def _update_status(self, paired):
-        button = self.button
-        icon = button.icon_paired if paired else button.icon_unpaired
-        button.setIcon(QIcon(icon))
+        if hasattr(self, 'button'):
+            button = self.button
+            icon = button.icon_paired if paired else button.icon_unpaired
+            button.setIcon(QIcon(icon))
 
     def query_choice(self, msg, labels):
         self.done.clear()